The present invention relates a method for linking a digital description of a traffic route network to at least one additional digital description of a traffic route network and a location database with a link to at least one additional location database, in particular for determining routes between traffic route network locations contained in the location database and in the at least one additional location database, in which a location database provided for decoding digitally coded traffic messages contains the necessary locations for the decoding of digitally coded traffic messages as location codes with a traffic route and references to adjacent locations situated on the same traffic route being assigned to each location code in one record.
The radio data system (RDS) makes possible an additional, inaudible transmission of data simultaneously with radio programs in one data channel. Specifications of the radio data system for ultrashort wave radio are established among other places in publication Tech. 3244-E, March 1984, of the European Broadcasting Union (EBU). Radio receivers with suitable RDS decoders can receive and decode transmitted data in addition to the radio reception with the same receiving component. Thirty-two groups, each with 104 bits, are provided for transmission, with each of the transmitted groups being assigned a specific service. Group 8a is currently provided for the transmission of digitally coded traffic messages. Such traffic messages fundamentally can also be transmitted via other transmission systems, such as DAB (Digital Audio Broadcasting) and mobile radio systems.
The structure and coding of these traffic messages are established in CEN Draft pr. ENV/278/4/1/0011 which was based on the standards recommendation ALERT C, published by the RDS ATT ALERT Consortium, November 1990. The essential elements of such a traffic message are the location of the event (Location) and the event (Event). The data are cataloged, that is, a unique code is assigned to each traffic-relevant location and to each traffic-relevant event. The linking of the locations in the location table along existing roads represents the course. Required for use of the traffic reporting channel, in addition to the conventional receiving device with an RDS decoder, are TMC (traffic message channel) devices for decoding, storing, further processing, and outputting of traffic messages.
The location databanks required for the decoding of traffic messages are made up of lists of junctions, interchanges, expressway merge points, exits to parking places, and similar locations with all locations situated on a road (expressway, highway) being linked together by references. Since not all locations are accessible from both directions, the linkages are given for both directions separately through a predecessor and a successor for each location being entered in the location database. If a location does not have a successor, for example, at the end of a road, this fact is designated by a special entry. Locations, such as intersections, for example, which are situated on multiple routes, are entered for each of these routes with different location codes.
This location database structure, in which thus no relationships are indicated between the same locations on different routes, is sufficient for the decoding of the traffic messages. For outputting the decoded traffic messages, this does indeed provide, for a particular location, a particular name which is indicated in coded form upon every occurrence of the same place in the location database. This information however only serves for outputting the actual name as an alphanumeric display or as voice output.
One advantage of the digitally coded traffic messages is that they do not exist as voice samples but rather as data which can be processed in multiple ways. In this way, for example, a selection of traffic messages is possible so that the automobile driver obtains only those traffic messages which relate to his prospective route and detours which may come into consideration.
It is nevertheless a prerequisite for a selection of this kind that the prospective route be known to the computer which is to perform this selection. This can take place through a manual inputting of the prospective route. Another possibility is for the destination to be input and for the computer to be allowed to determine the route.
Suitable calculating procedures are known and are available, for example, in PC programs. For this purpose, however, a road map is needed which contains the relevant roads and intersections and the distances between the intersections and other locations.
The use of this kind of a location database of route search is possible according to German Patent Application No. 196 06 010 in that there are cross references to those locations which are situated on two routes and thus represent intersections. With this, however, a route search between locations which are listed in different location databases is still not possible. This may occur, for example, in the case of route searches which span national borders since the compilation of location databases generally takes place by country. However, this problem can even occur within one country if, for example, regional location databases supplement a country-wide database since the latter represents the network of roads in the urban areas only inadequately or different traffic route networks (automobile, train, etc.) are described by the databases.
An object of the present invention therefore is to provide a method for linking digital descriptions of traffic route networks and a suitable location database for linking with at least one additional location database, in particular for the determination of routes between locations contained in the location database and at least one additional location database.
This object is achieved in the method according to the present invention in that records of those locations, which have at least one adjacent location in at least one of the additional descriptions of traffic route networks, have at least one reference to at least one such adjacent location.
The location database according to the present invention provides that the records of those locations, which have at least one adjacent location in at least one of the additional location databases, contain at least one reference to at least one such adjacent location including a location database reference. It is preferably provided that the location database reference is composed of a country number and a location database number.
The present invention makes possible a search for routes spanning location databases, for example within the European traffic route network, without fundamentally changing the structure of the location database as it is necessary for decoding traffic messages. The route search as such is not an object of the present invention. Various methods are known for performing such searches. It is merely necessary that information in the location databank concerning the geographic situation of the locations be present, for example their geographic coordinates. The application of the present invention is not limited to a search for routes. Thus, for example, coding and decoding of messages which span location databases can be undertaken using the present invention.
To be able to distinguish a location contained as a reference in the location database from other information, one advantageous embodiment of the location database according to the present invention provides that the location database reference be designated as such by a reserved code word. This can be composed, for example, of six leading 1""s.
A first embodiment of the database according to the present invention, in which each record, in addition to a data field for that location and other data fields, has one data field each for the designation of adjacent locations, is composed of the data fields for designating the adjacent locations, each being designed for receiving the reserved code word, the location database reference, and the location code of an adjacent location situated in one of the additional location databases.
In this embodiment, two locations from a different location database can be referenced in a record of a location with the direction being taken into consideration. The expansion is made only at these transition points, all other location databases remaining unchanged.
A second embodiment of the location database according to the present invention, in which each record, in addition to a data field for the particular location and other data fields, contains a data field for the designation of each adjacent location, is composed of the data fields for the designation of adjacent locations, each being designed for receiving the reserved code word and the location database reference and, in the event of the presence of an adjacent location situated in one of the other location databanks, an additional data field containing its location code.
In this embodiment, in place of the end code (the particular location is situated at the end of one of the roads included in the particular location database), the location database reference is inserted. Since only the ends of stretches of routes are considered here, the addition of the location code at the end of a record is sufficient. This embodiment has the advantage that it corresponds to the structures suggested in German Patent Application No. 196 06 010. Complex intersection situations can be described using known location database elements.
In a third embodiment of the location database according to the invention in which each record, in addition to a field for the particular location and other data fields, contains a field for the designation of adjacent locations, it is provided that the data fields for the designation of adjacent locations be filled corresponding to the part of the network of routes represented by the location database and that the location database reference and the location code of an adjacent location situated in one of the additional location databases be filed in a data field for cross references.
In this embodiment, the entries provided for decoding the traffic messages, in particular also the end code, remain unchanged. The cross reference is implemented in each case through appending data fields to the records affected. The embodiment has the advantage that it does not change the original location database. In this embodiment, even complex intersection situations can be described. It can be provided in the first through the third embodiments that the data fields for designating adjacent locations have variable lengths.